The present invention relates to an electrophotographic copying machine and, more particularly, to a device for detecting the position of an optical scanning system for an electrophotographic copying machine.
Conventionally, an electrophotographic copying machine produces an electrostatic latent image on an optical-sensitive member. The latent image corresponds to an image on a copy object such as a manuscript or book. Toner particles are adhered to the latent image, so that the latent image becomes visible to form a copied image.
To form the latent image on the optical-sensitive member, while the optical-sensitive member is charged uniformly, a reflected image from the copied object is projected upon the optical-sensitive member, so that the charges at the light projected portions are released to produce voltage differences between the light projected portions and the light non-projected portions. The electrostatic latent image is thus produced.
As the optical-sensitive member is rotated to which the optical image from the object should be projected, the object must be subjected to optical scanning. To cause the optical scanning on the object disposed on an object plate, the object plate is moved in synchronization with the rotation of the optical-sensitive member while the optical scanning system including lenses and mirrors is fixedly positioned. In the alternative, at least a part of the optical scanning system is moved along the object plate while the object plate is fixed.
Thus, the object plate or the part of the optical scanning system must be moved in synchronization with the rotation of the optical-sensitive member.
Conventionally, a plurality of microswitches and sensors is positioned along the path of the object plate or the part of the optical scanning system to detect the position of the optical scanning system and the part. The positions of the microswitches and the sensors are adjusted because they must be positioned at the initial position and the return position of the object plate or the part of the optical scanning system. Such adjustment steps are rather complicated, so that it is desired to present a simple position detecting system.